This was posted by my vet on Facebook. It's a long and distreasing read, but please, if you're one of the people walking your dogs in this heat, don't do it 
Heatstroke Warning for Dog Owners
Heat Stroke – what’s the big deal?
There are a lot of posts warning dog owners to be careful in the hot weather, but still there are dogs being exercised at inappropriate times of the day. When the weather is as hot as it is, as suddenly as it is, it may even be inappropriate to exercise your dog at all.
Why does everyone make such a fuss about dogs getting too hot? Clearly there are far too many owners who don’t understand the importance of the warnings. The fact is, excess heat can all too easily be fatal – yes fatal – your dog will die. Not just die, they will die a particularly horrible death.
In all the many warnings and articles that are around there doesn’t seem to be any description of the process of heatstroke and how it actually causes a dog to die. Well maybe they should, because perhaps then owners would be a bit more serious in their efforts to protect their dogs.
If you are of an easily offended disposition, don’t continue reading. However, if you are of an easily offended disposition and still take your dog out in the heat then continue reading and be offended but educated. You have been warned
Today a dog died of severe heat stroke – exercised at 9 o’clock in the morning. If it was a child, the parents would be convicted of man slaughter and sent to prison. The long coated dog was being exercised in the local park at 9am this morning – it was already 21˚C. The owners where throwing a ball for the dog. Our loyal faithful friends will still pander to our requests of going with us for a walk or fetching the ball thrown even when they are under extreme stress of excessive heat. They don’t know to self regulate, because their pack leader has instructed them to walk with them or chase a ball etc.
I turned up to the local park to park my car and walk to work. It was in the car park that I discovered the dog with the owners next to their car, suffering from severe heat stroke. The scene was; the dog lying flat out on his side, semi-conscious, with extreme panting. His mouth and tongue were swollen up and a dark red/purple colour, there was a white frothy coating of saliva, the tongue and gums being fairly dry. The owners were trying to get the dog to drink some water, but the dog was entirely unable to do so. His belly was distended from panting and gulping air; this in itself can then restrict breathing.
I was not equipped to take the dog’s temperature, but I could feel it was dangerously high. His pulse however was unusually slow. I had water in my car and dowsed the dog’s coat down and we wetted a towel to stretcher the dog in to the car and for him to lay on in transit.
The dog was not registered with my practice, so I instructed the owner to take the dog to their own vet immediately.
Once I had finished my shift at work, I phoned the owner’s vet to see if they could tell me how the dog was. He was dead. A 5 year old, fit and healthy dog - dead. A death that was completely preventable. I asked the vet for detaila explaining that I was going to write this post. They were in support as long as names weren’t mentioned. Names are irrelevant, as this story will be happening all over the country.
The owners took the dog straight to their practice were he was treated immediately. His body temperature was just shy of 42˚C. A normal temperature range for a dog is 38.3˚C to 39.2˚C, a rise of just 1 – 2˚C can have major effects on the dog’s body systems. The nurses commenced cooling of the dog and the vet put him on a drip with rapid infusion of fluids and electrolytes. However, within 10 – 15 mins of being admitted the dog began to seizure. Seizures are caused when the electrical impulses in the brain misfire and cause like an electrical storm in the brain so the muscle fibres of the body rapidly twitch uncontrollably. In this case, the excess heat in the brain disturbs the electrical impulses. This is an added issue as the activity of the muscles then acts to increase the dog’s temperature even more. It was at this point that the vet went to gain consent to administer anaesthetic to the dog to try and reduce the seizure and lower the respiratory rate. But as the vet was talking to the owner, approximately 20 mins after arriving at the practice, the dog began to vomit and pass diarrhoea. The vomit and diarrhoea was full of blood. This even to the untrained reader, you can appreciate is bad news.
Once this was discovered, the dog’s gums were checked and small red/black spots were present, along with areas of bleeding on the abdomen. At this point the vet had to return to the owners and request consent for euthanasia.
The dog was suffering from disseminated intravascular coagulopathy. This is a fancy veterinary term that means the dog’s body systems was unable to clot his blood and therefore he was bleeding internally. In the veterinary world, it is nicknamed Death Is Coming. The process is not fully understood, but it is thought that the excess temperature prevents the body from performing the myriad of chemical reactions that allow it to function normally. Loosely, this causes the body to activate clotting, causing hundred of clots within the body. Once all the clotting factors are used up, the blood can no longer clot, so widespread haemorrhage ensues. It causes major organ failure; the kidneys, the liver, the heart and the lungs cease to function effectively. With a bit of luck, the dog is unconscious by this stage, as this must be hugely uncomfortable and a terrifying death.
For all those dog owners who think this was because the dog was chasing a ball and that is why he overheated, this can happen with your dog sat in the sun in the garden. It can take up to 60 days for a dog to acclimatise to a change in climate. I am pretty sure 60 days ago it was pouring with rain.
Once the dog becomes mildly overheated, unless they are cooled, they will continue to overheat. Dogs cannot sweat effectively and can only really lose body heat through panting. The process of panting can in itself cause excess body temperature if it is prolonged or laboured.
So, if you think it is too hot to put a thick coat on and go for a run, don’t make your dog do the same. If you think it is too hot to sit in direct sunshine for more than a few minutes whilst wearing a woolly jumper, then don’t make your dog do so. If it is too hot to stand on the pavement with your shoe and socks off, then don’t make your dog walk on it. If you don’t want to sit in your car without the air con on even if you have all windows wound down, don’t leave your dog in the car. If you are ever in any doubt of how to care for your dog in the warm or hot weather, speak your local vet practice. Better to speak to them now than your vet speaking to you to request consent for euthanasia.